[PT031AAO1], Technical Note, Thomas Alva Edison, June 22nd, 1887


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[PT031AAO1], Technical Note, Thomas Alva Edison, June 22nd, 1887

Editor's Notes

[witnessed by Mina 11/16/87] Dyer-- Here is a general sweeping Caveat I want to file in the office for dating purposes I suppose of course they will reject it as not accordin to rules; but it will get patent office stamp on it & can lay there. Improvements in Transformers. I use thin sheet iron punched from sheet in the form of an open ring [drawings] a large number are laid together & insulated from each other by paper or a coating of varnish [drawings] A is a bobbin made in one piece from glass hard Rubber or other insulating material the material employed is one that is difficult to perforate by charges of high potential Hard Rubber is excellent for this purpose-- The bobbins are wound half of them having fine wire & the other half coarse wire the former for the primary & the latter for the secondary-- The bobbins are placed in the broken part of the iron ring & shoved over it first a fine wire then a large wire bobbin & so on until the ring is covered with bobbins. They are afterwards so connected together that all the coarse wires Bobbins form a complete windin & the fine wire ones another complete winding-- after this is done all the bobbins are pressed very close to each other & then by a chisel shaped tool working on the edges of the thin iron plate rings various ones are advanced to different distances thus closing the ring completely the total break being now distributed throughout the centre ring and are infinitesimal at any one point. The advantage of this form is first that a large amount of iron can be used in the usual way 2nd The Lines of force pass through practically continuous piece of iron 3rd The trouble of winding a closed ring is obviated. 4th The bobbins being placed sepearately on the core & the wire being on a complete piece of material of high disruptive power to currents of high potential, it is not so liable to be destroyed by lightning. The ordinary converters are very subject to destruction by lightning the primary & secondary acting as a condenser-- but with bobbins whose parts are integral the flash must be of enormous potential to burst through the material, while it would find no difficulty were cotton insulation even covered with viscous materials 5 another advantage is that should any bobbin be destroyed by lightning the chisel may be used to bring all the iron rings back to a commonn opening & the bobbin replaced.-- A method I propose to prevent the destruction of Converters in a system by lightning is as follows [2 drawings] Another Method is to use condensers connected to earth which will be more easily disrupted by lightning than the coils of the converter & yet sufficiently non disruptive to remain intact with 100 percent more electromotive force than the primary current of high potential. [drawing] Method of Tanning Leather. This method consists in driving the tanning liquor through the hide by electrical endmose. The cell containing the tanning liquor is divided electrically in two parts by the hide The positive electrode of Carbon is in the liquor on one side of the hide & the negative Carbon is on the other side, when a battery or other source of electricity is connected to the two electrodes a current of E is established through the pores of the hide and endmose is set up the liquor being rapidly carried from the positive to the negative through the pores; and the liquor in one half begins to fall while the liquor in the other half commences to rise then as much tanning liquor is passed through the hide in 4 hours as would naturally pass in a week in the ordinary manner without the assistance of electrcity-- Improvement in Machines for seperating magnetic & diamagnetic substances by altering the trajectory of their fall by a magnet. The improvement consists in causing the finely divided particles to tall in a thin sheet before the poles of the magnet, while in a vacuum so that the air will not interfere to deflect the light particles from falling in a straight line when not magnetic. [drawings] Magnetic Bridge for measuring the magnetic conductivity of magnetic substances & for the detection of flaws in steel & iron articles shafts etc [drawing] X is the large electro magnet for magnetizing the Bridge N M are constant & are formed of pure iron d e is the bridge piece broken in the centre to create a magnetic field in this is a magnetized needle provided with pointer & scale or mirror & Lamp stand & scale The needle is held in position by a torsion wire. A is a section of iron to be measured & B is s standard bar when M N are perfectly equal conductors of magnetic lines & A & B the same; There is no field of force formed in the bridge at C hence the needle is not deflected but should the iron at A have the slightest impurity it will not conduct the magnetic lines so well as the pure bar B hence the balance of Lines will be destroyed and the needle deflected in one direction, should the iron be known to be pure but a cavity was in it, it would for this reason fail to conduct as well. To those acquainted with the Electrical Bridge it will be at once seen that with a number of standard bars known to be pure & of different sizes The magnetic resistance of any magnetic substance placed at A even the resistance of air space etc can be accurately ascertained. This apparatus arranged in a proper manner can be made to rapidly measure the perfection of car wheel axles also the quantities of steel as they depend on the Carbon & structural arrangement."



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Thomas A. Edison Papers, School of Arts and Sciences, Rutgers University
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